1. Field of the Invention
The present invention relates to a liquid crystal display, and particularly relates to a liquid crystal display of a parallax barrier system.
2. Description of the Background Art
There has been proposed a liquid crystal display (dual-screen LCD) capable of displaying dual images on a display screen so that one of the images is visually recognized in a left direction and another one of the images is visually recognized in a right direction.
Such a dual-screen LCD is applied to a display for providing different images to viewers at right and left positions, such as a driver and a passenger in a vehicle, or a three-dimensional (3D) display for providing different images to right and left eyes of a viewer so as to form a three-dimensional image.
Such a dual-screen LCD is realized by optically separating pixels providing an image into pixels visually recognized in a specific direction and pixels visually recognized in another specific direction. It is also possible to display multiple images by modifying separating means so that pixels are visually recognized in multiple directions without limiting the directions of visually recognizing the pixels (lines of sight) to the two right and left directions.
While there is proposed a technique with use of a lens or the like as the means for optically separating lines of sight, a parallax barrier technique has been getting popular, in which lines of sight of visually recognizing pixels are separated by a light blocking film (parallax barrier) provided with an opening (transmissive portion) in correspondence with each of pixels providing different images.
For example, Japanese Patent Application Laid-Open No. 2007-072476 discloses a mechanism in which light having transmitted a color filter (CF)-black matrix (BM) surface is blocked by a parallax barrier to travel only in a specific line of sight, so as to provide an image visually recognized in a left direction and another image visually recognized in a right direction on a display screen of a liquid crystal display.
Such a parallax barrier has been conventionally formed by preparing a glass substrate provided with a parallax barrier separately from a liquid crystal cell and attaching the glass substrate onto an outer surface of the liquid crystal cell. On the other hand, Japanese Patent Application Laid-Open No. 2007-072476 proposes a method of forming a parallax barrier directly on a CF glass surface.
According to Japanese Patent Application Laid-Open No. 2007-072476, the liquid crystal cell is formed after having formed both a light blocking film serving as the black matrices and a light blocking film serving as the parallax barrier respectively on front and rear surfaces of a CF substrate. To the contrary, Japanese Patent Application Laid-Open No. 2011-128547 discloses a method of initially forming a liquid crystal cell, secondly thinning a CF substrate, and then forming a parallax barrier.
Japanese Patent Application Laid-Open No. 09-166777 (1997) discloses employing double-layered light blocking films serving as a black mask (black matrices) formed on a CF glass surface, in order to suppress generation of pinholes due to adhesion of dust or the like. In this method, the lower light blocking film is formed and cleaned to remove dust and the like before the upper light blocking film is formed.
As disclosed in Japanese Patent Application Laid-Open No. 2007-072476 and Japanese Patent Application Laid-Open No. 2011-128547, in the configuration in which the parallax barrier is formed directly on the CF glass surface, the light blocking film serving as the parallax barrier is provided on the rear surface of the CF substrate (that is, a front surface of a display).
However, in the conventional method of forming a light blocking film, the obtained light blocking film is possibly provided with pinholes or defective patterns due to foreign substances having been left on the glass substrate prior to the formation of the light blocking film or foreign substances adhering to the glass substrate during the formation.
Such pinholes and defective patterns may cause bright spots or variation in brightness, which lead to deterioration in display quality. Additionally, the light blocking film exposed on the outermost surface is likely to be provided with cracks and the like after the formation of the light blocking film. The light blocking film having such cracks deteriorates in its functions, which also leads to deterioration in display quality.
Such pinholes and defective patterns due to foreign substances are problematically recognized also in Japanese Patent Application Laid-Open No. 09-166777 (1997). However, Japanese Patent Application Laid-Open No. 09-166777 (1997) discloses the invention relating to light blocking films in a CF substrate, serving as the black mask provided inside a cell of a liquid crystal panel, and does not relate to a light blocking film formed on the rear surface of a CF substrate. According to Patent Application Laid-Open No. 09-166777 (1997), the black mask is located inside the cell after the cell of the liquid crystal panel is formed. Patent Application Laid-Open No. 09-166777 (1997) does not have the problem caused by the light blocking film exposed outside the cell as in Japanese Patent Application Laid-Open No. 2007-072476 and Japanese Patent Application Laid-Open No. 2011-128547. Patent Application Laid-Open No. 09-166777 (1997) neither discloses nor suggests such a configuration for solving the problem of cracks formed in a light blocking film (parallax barrier) provided outside a cell of a liquid crystal panel.